Digital full duplex over single channel solution for small cell backhaul applications

ABSTRACT

To provide for higher data rates, a wireless back haul network for connecting small cell base stations to a core network can be implemented using full-duplex over single channel communications. The difficulty with full-duplex over single channel communications, and the reason why it has not become common place in wireless and mobile communication standards to date, is the significant interference that the receiver of a full-duplex communication device will generally experience from the full-duplex communication device&#39;s own transmitter transmitting over the same channel that the receiver is to receive signals. This interference is referred to as self-interference because the interference experienced by the receiver originates from its own paired transmitter. The present disclosure describes embodiments of an apparatus and method that provide sufficient self-interference cancellation in a compact and power efficient manner for a small cell wireless backhaul network.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/091,324, filed Apr. 5, 2016 (now U.S. Pat. No. 9,894,539), whichclaims the benefit and priority to U.S. Provisional Patent ApplicationNo. 62/143,717, filed Apr. 6, 2015, now expired. Each of the above namedapplications is hereby incorporated by reference herein.

TECHNICAL FIELD

This application relates generally to small cell base stations,including backhaul applications for small cell base stations.

BACKGROUND

A conventional cellular network is deployed as a homogenous network ofmacrocell base stations. The macrocell base stations may all havesimilar antenna patterns and similar high-level transmit powers. Toaccommodate increases in data traffic, more macrocell base stations canbe deployed in a homogenous network, but such a solution is oftenunattractive due to increased inter-cell interference on the downlinkand due to the high costs associated with site acquisition for newlydeployed macrocell base stations.

Because of these drawbacks and others, cellular network operators areturning to heterogeneous networks to meet the demands of increased datatraffic. In heterogeneous networks, small cell base stations are used toprovide small coverage areas that overlap with, or fill in gaps of, thecomparatively larger coverage areas provided by macrocell base stations.The small coverage areas are typically provided in areas with high datatraffic (or so called hotspots) to increase capacity. Examples of smallcell base stations include, in order of decreasing coverage area,macrocell base stations, picocell base stations, and femtocell basestations or home base stations.

There has been a steady increase in the deployment of small cell basestations. In the near future, it is expected that in some areas therewill be orders of magnitude more small cell base stations deployed thanmacro cells. With such high densities (e.g., tens of small cell basestations per square kilometer), the small cell backhaul network used toconnect the small cell base stations to the core network, Internet, andother services will be a challenge.

Installing high-capacity, low-latency wired connections from the smallcell base stations to the core network would require an exorbitantcapital expenditure on the part of network operators. A moreeconomically feasible approach is to implement a wireless backhaulnetwork to link the small cell base stations to the core network. Forexample, such a wireless backhaul network can link the small cell basestations to the core network via existing macro base stations thatalready have wired access to the core network. However, the data trafficrate on the wireless backhaul can be very high given that a typicalmacro base station may be required to relay backhaul data for tens ofsmall cell base stations. Thus, the design and implementation of highdata rate wireless backhaul transmissions is important.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate the present disclosure and, togetherwith the description, further serve to explain the principles of thedisclosure and to enable a person skilled in the pertinent art to makeand use the disclosure.

FIG. 1 illustrates an exemplary heterogeneous cellular network withsmall cell base station that provide small coverage areas that overlapwith, or fill in gaps of, macrocell base stations in which embodimentsof the present disclosure can be implemented.

FIG. 2 illustrates an exemplary high-level block diagram, of animplementation of a small cell base station in accordance withembodiments of the present disclosure.

FIG. 3 illustrates an exemplary high-level block diagram of componentsin a baseband processor of a small cell base station in accordance withembodiments of the present disclosure.

FIG. 4 illustrates a flowchart of a method for a small cell base stationto perform self-interference cancellation at baseband in accordance withembodiments of the present disclosure.

FIG. 5 illustrates a block diagram of an example computer system thatcan be used to implement aspects of the present disclosure.

The present disclosure will be described with reference to theaccompanying drawings. The drawing in which an element first appears istypically indicated by the leftmost digit(s) in the correspondingreference number.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the disclosure. However, itwill be apparent to those skilled in the art that the disclosure,including structures, systems, and methods, may be practiced withoutthese specific details. The description and representation herein arethe common means used by those experienced or skilled in the art to mosteffectively convey the substance of their work to others skilled in theart. In other instances, well-known methods, procedures, components, andcircuitry have not been described in detail to avoid unnecessarilyobscuring aspects of the disclosure.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

For purposes of this discussion, the term “module” or “block” (e.g., ablock in a block diagram) shall be understood to include software,firmware, or hardware (such as one or more circuits, microchips,processors, and/or devices), or any combination thereof. In addition, itwill be understood that each module or block can include one, or morethan one, component within an actual device, and each component thatforms a part of the described module or block can function eithercooperatively or independently of any other component forming a part ofthe module or block. Conversely, multiple modules or blocks describedherein can represent a single component within an actual device.Further, components within a module or block can be in a single deviceor distributed among multiple devices in a wired or wireless manner.

1. Overview

To provide for higher data rates, a wireless backhaul network forconnecting small cell base stations to the core network can beimplemented using full-duplex over single channel communications. Aduplex communication system includes two transceivers that communicatewith each other over a channel in both directions. There are two typesof duplex communication systems: half-duplex communication systems andfull-duplex communication systems. In half-duplex communication systems,the two transceivers communicate with each other over the channel inboth directions but only in one direction at a time; that is, only oneof the two transceivers transmits at any given point in time, while theother receives. A full-duplex communication system, on the other hand,does not have such a limitation. Rather, in a full-duplex communicationsystem, the two transceivers can communicate with each other over thechannel simultaneously in both directions.

Wireless communication systems often emulate full-duplex communication.For example, in some wireless communication systems two transceiverscommunicate with each other simultaneously in both directions using twodifferent carrier frequencies or channels. This scheme, wherecommunication is carried out simultaneously in both directions using twodifferent carrier frequencies, is referred to as frequency divisionduplexing (FDD). FDD is said to only emulate full-duplex communicationbecause FDD uses two half-duplex channels rather than a single channelto accomplish simultaneous communication in both directions.

Although emulated full-duplex communication using FDD allows forsimultaneous communication in both directions, it requires two channels.True full-duplex communication eliminates the need for one of these twochannels, resulting in increased spectrum efficiency and the ability toprovide higher data rates. The difficulty with true full-duplexcommunication, and the reason why it has not become common place inwireless and mobile communication standards to date, is the significantinterference that the receiver of a full duplex communication devicewill generally experience from the full-duplex communication device'sown transmitter transmitting over the same channel that the receiver isto receive signals. This interference is referred to as selfinterference because the interference experienced by the receiveroriginates from its own paired transmitter.

For example, in a wireless backhaul network for small cell basestations, backhaul signals can be transmitted at power levels at 10 dBmand backhaul signals can be received at power levels at or below −60dBm. At these levels, the self-interference needs to be reduced by atleast 10 dBm—(−60 dBm)=70 dBm, not accounting for the receiver noisefloor, to allow for information to be recovered from the receivedsignals. Not only is the amount of self interference that needs to becanceled a challenging task, but also providing such cancellation in acompact and power efficient manner also provides challenges.

Described below are embodiments of an apparatus and method that providesufficient self-interference cancellation in a compact and powerefficient manner for a small cell wireless backhaul network. It shouldbe noted that embodiments of the apparatus and method can be furtherused to communicate over other networks besides backhaul networks andare not limited to implementations within small cell base stations butcan be used within a wide variety of other communication devices.

2. Exemplary Operating Environment

FIG. 1 illustrates an exemplary heterogeneous cellular network 100 inwhich embodiments of the present disclosure can be implemented.Heterogeneous cellular, network 100 can be operated in accordance withany one of a number of different cellular network standards, includingone of the current or yet to be released versions of the long-termevolution (LTE) standard and the worldwide interoperability formicrowave access (WiMAX) standard.

As shown in FIG. 1, heterogeneous cellular network 100 is distributedover macrocells 102-106 that are each served by a respective macrocellbase station 108-112. Macrocells 102-106 are geographically joinedtogether to enable user terminals (UTs) 114 (e.g., mobile phones,laptops, tablets, pagers, smart watches, smart glasses, or any otherdevice with an appropriate wireless modem) to wirelessly communicateover a wide area with a core network 116 via macrocell base stations108-112. Macrocell base stations 108-112 are coupled to the core networkby a wired backhaul network 118.

As further shown in FIG. 1, macrocells 102-106 are overlaid with severalsmall cells 120-130 that are each served by a respective small cell basestation shown at the center of each small cell. The small cell basestations can be deployed in areas with high data traffic to increasecapacity or in areas with limited or no coverage provided by macrocellbase stations 108-112. Although not shown for each small cell basestation, the small cell base stations are further coupled to corenetwork 116 via a wireless back haul network.

For example, the small cell base stations of small cells 126 and 128 areshown communicating over the wireless backhaul network viasingle-channel full-duplex communication signals 132 and 134,respectively. Single-channel full-duplex communication signals 132 and134 are specifically sent to and received from macrocell base station110, which uses wired backhaul network 118 to relay the backhaul data ofsmall cells 126 and 128 to and from core network 116. In otherembodiments, single-channel full-duplex communication signals 132 and134 are directly sent to and received from core network 116 by the smallcell base stations of small cells 126 and 128, respectively. In otherembodiments, wired backhaul network 118 can be replaced with a wirelessbackhaul network or replaced in part by a wireless back haul network.

Referring now to FIG. 2, an exemplary high-level block diagram 200 of animplementation of one or more of the small cell base stations in FIG. 1is illustrated in accordance with embodiments of the present disclosure.As shown in block diagram 200, the small cell base station includes atleast one cellular antenna 202, a cellular transceiver 204, a basebandprocessor 206, a wireless backhaul transceiver 208, a backhaul transmit(TX) antenna 210, and a backhaul receive (RX) antenna 212. Wirelessbackhaul transceiver 208 includes an RF transmitter 214 coupled to apower amplifier (PA) 216 and an RF receiver 218 coupled to a low-noiseamplifier (LNA) 220. It should be noted that FIG. 2 is provided by wayof example and not limitation. One of ordinary skill in the art willrecognize that other implementations of the small cell base station arepossible without departing from the scope and spirit of the presentdisclosure.

In operation, baseband processor 206 can be used to implement, at leastin part, the radio protocol stack for one of several different cellularstandards, including LTE and WIMAX, and can be used as an interface forpassing data between wireless backhaul transceiver 208 and cellulartransceiver 204.

For example, data received via cellular antenna 202 from a UT served bythe small cell base station can be passed to baseband processor 206.Baseband processor 206 can extract data from the uplink transmissionreceived from the UT in accordance with a cellular radio protocol stackand map the data to a series of complex symbols to form a transmitbaseband signal. Baseband processor 206 can then pass the transmitbaseband signal to RF transmitter 214 and power amplifier 216. RFtransmitter 214 can perform, among other things, up-conversion of thetransmit baseband signal to a radio frequency (RF) carrier frequency,and power amplifier 216 can subsequently amplify the up-convertedtransmit baseband signal or transmit RF signal for wirelesstransmission, via backhaul TX antenna 210, over the wireless backhaulnetwork. As discussed above, in regard to FIG. 1, the small cell basestation can transmit the transmit RF signal to a macrocell base stationor directly to the core network.

Similarly, a receive RF signal received via backhaul RX antenna 212 overthe wireless backhaul network is first amplified by LNA 220 and thenpassed to RF receiver 218. RF receiver 218 can perform, among otherthings, down-conversion of the amplified receive RF signal to provide aseries of complex symbols that form a receive baseband signal. Basebandprocessor 206 can extract data from the symbols of the receive RF signaland provide the data to cellular transceiver 204 for transmission to theUT via cellular antenna 202.

The transmit RF signal and the receive RF signal, respectivelytransmitted and received over the wireless backhaul network by wirelessbackhaul transceiver 208, can be communicated over the wireless backhaulnetwork over the same time and frequency band. In other words, the twosignals can be communicated over the wireless backhaul network inaccordance with a single-channel full-duplex communication scheme. Thefrequency band can be a millimeter radio band between 30 GHz and 30 GHz,such as 60 GHz.

However, as noted above, the receive chain of wireless backhaultransceiver 208 (i.e., RF receiver 218 and LNA 220) will experiencesignificant interference from the transmitter chain of wireless backhaultransceiver 208 (i.e., RF transmitter 214 and PA 216), referred to asself-interference as shown in FIG. 2. For example, in the wirelessbackhaul network, transmit RF signals can be transmitted at or above 10dBm and receive RF signals can be received at power levels at or below−60 dBm. At these levels, the self-interference needs to be reduced byat least 10 dBm—(−60 dBm)=70 dBm, not accounting for the receiver chainnoise floor, to allow for information to be recovered from the receiveRF signals. Described below is an apparatus and method that providessufficient self-interference cancellation in a compact and powerefficient manner for the small cell base station in FIG. 2.

3. Self-Interference Cancellation at Baseband

Referring now to FIG. 3, an exemplary high-level block diagram 300 ofcomponents in a portion of baseband processor 206 of the small cell basestation of FIG. 2 is illustrated in accordance with embodiments of thepresent disclosure. As shown in block diagram 300, baseband processor206 includes a mapper/dc-mapper 302, a digital-to-analog converter (DAC)304, an analog-to-digital converter (ADC) 306, and a basebandself-interference canceller 308. It should be noted that FIG. 3 isprovided by way of example and not limitation. One of ordinary skill inthe art will recognize that other implementations of baseband processor206 are possible without departing from the scope and spirit of thepresent disclosure.

In operation, mapper/de-mapper 302 is configured to map data to betransmitted over the wireless backhaul network to a series of complexsymbols to provide a transmit baseband signal to RF transmitter 214.Before being provided to RF transmitter 214, the transmit basebandsignal can be converted from a digital signal to an analog signal viaDAC 304. In the opposite direction, a receive baseband signal from RFreceiver 218 can be first converted from an analog signal to a digitalsignal by ADC 306 and then provided to mapper/demapper 302 to de-mapcomplex symbols in the receive baseband signal.

However, prior to mapper/demapper 302 receiving the digital complexsymbols that make up the receive baseband signal, basebandself-interference canceller 308 can be used to cancel self-interferencefrom the transmit RF signal in the receive RF signal as explained abovein regard to FIG. 2. More specifically, baseband self-interferencecanceller 308 includes an RF impairment compensator 310 and a digitalcanceller 312. RF impairment compensator 310 can distort the transmitbaseband signal based on the analog components in the transmitter chainof wireless backhaul transceiver 208 (i.e., RF transmitter 214 and PA216).

In general, these analog components in the transmitter chain distort thetransmit baseband signal in both linear and non-linear ways, while alsoadding noise. RF impairment compensator 310 includes hardware to atleast adaptively estimate the linear and non-linear distortions that thetransmitter chain of wireless backhaul transceiver 208 introduces intothe transmit baseband signal and uses this estimate to similarly distorta copy of the transmit baseband signal. RF impairment compensator 310can further scale and delay the distorted transmit baseband signal tomatch the self-interference in the receive baseband signal. Thedistorted copy of the transmit baseband signal is then provided todigital canceller 312, which effectively subtracts the distorted copy ofthe transmit baseband signal from the receive baseband signal providedby ADC 306. Thus, baseband self-interference canceller cancelsself-interference from the transmit RF signal in the receive RF signalat baseband.

In one embodiment, RF impairment compensator 310 can adaptively estimatethe linear and non-linear distortions that the transmitter chain ofwireless backhaul transceiver 208 by sending a range of input powerlevels through the transmitter chain and measuring the correspondingrange of output power levels from the transmitter chain. The input powerlevel may measure a RF signal, which may be generated from a basebandsignal. The baseband signal may be a complex signal that comprises anin-phase component and a quadrature-phase component. In addition, RFimpairment compensator 310 can adaptively estimate the linear andnon-linear distortions that the transmitter chain of wireless backhaultransceiver 208 by measuring a relative change in the phase relationshipbetween the corresponding baseband component signals I and Q afterhaving been processed by the transmitter chain.

No self-interference cancellation need be performed in the analog domainat RF. For example, no-self interference need be performed prior to LNA220 in FIG. 2. Saturation of LNA 220 is prevented by using separateantennas to transmit and receive over the wireless backhaul network.More specifically, as discussed above in regard to FIG. 2, backhaul TXantenna 210 is used to transmit over the wireless backhaul network andbackhaul RX antenna 212 is used to receive over the wireless backhaulnetwork. Separation between the antennas provides some level ofisolation, which can reduce self-interference by a sufficient amount toprevent LNA 220 from becoming saturated due to self-interference. Inaddition, backhaul TX antenna 210 and backhaul RX antenna 212 can beimplemented as directional antennas (as opposed to omni-directionalantennas) to further limit self-interference. Because no selfinterference cancellation is done in the analog domain at RF,self-interference cancellation is performed in a compact and powerefficient manner.

Referring now to FIG. 4, a flowchart 400 of a method for a small cellbase station to perform self-interference cancellation at baseband isillustrated in accordance with embodiments of the present disclosure.The method of flowchart 400 can be implemented by a small cell basestation configured as shown in FIGS. 2 and 3. However, it should benoted that the method can be implemented by other small cell basestations with different configurations.

The method of flowchart 400 begins at step 402. At step 402, the smallcell base station up-converts and amplifies a transmit baseband signalto provide a transmit RF signal for wireless transmission via a backhaultransmit antenna. The up-conversion and amplification are performedusing analog components that add both linear and non-linear distortionsto the transmit baseband signal as well as noise.

At step 404, the small cell base station amplifies and down-converts areceive RF signal wirelessly received via a backhaul receive antenna toprovide a receive baseband signal. The receive RF signal is wirelesslyreceived over the same time and frequency band that the transmit RFsignal is transmitted in accordance with a single-channel full-duplexwireless backhaul communication scheme. As a result, the receive RFsignal includes self-interference from the transmit RF signal.

At step 406, the small cell base station digitally distorts a copy ofthe transmit baseband signal based on an estimate of the linear andnon-linear distortions associated with the analog components used toup-convert and amplify the transmit baseband signal to provide thetransmit RF signal. The distorted copy of the transmit baseband signalcan be further scaled and delayed at step 406 to better match theself-interference in the receive baseband signal.

At step 408, the small cell base station cancels self-interference inthe receive baseband signal based on the digitally distorted copy of thetransmit baseband signal. The cancellation can be performed in thedigital domain.

4. Example Computer System Environment

It will be apparent to persons skilled in the relevant art(s) thatvarious elements and features of the present disclosure, as describedherein, can be implemented in hardware using analog and/or digitalcircuits, in software, through the execution of instructions by one ormore general purpose or special-purpose processors, or as a combinationof hardware and software.

The following description of a general purpose computer system isprovided for the sake of completeness. Embodiments of the presentdisclosure can be implemented in hardware, or as a combination ofsoftware and hardware. Consequently, embodiments of the disclosure maybe implemented in the environment of a computer system or otherprocessing system. An example of such a computer system 500 is shown inFIG. 5. Blocks depicted in FIGS. 2 and 3 may execute on one or morecomputer systems 500. Furthermore, each of the steps of the methoddepicted in FIG. 4 can be implemented on one or more computer systems500.

Computer system 500 includes one or more processors, such as processor504. Processor 504 can be a special purpose or a general purpose digitalsignal processor. Processor 504 is connected to a communicationinfrastructure 502 (for example, a bus or network). Various softwareimplementations are described in terms of this exemplary computersystem. After reading this description, it will become apparent to aperson skilled in the relevant art(s) how to implement the disclosureusing other computer systems and/or computer architectures.

Computer system 500 also includes a main memory 506, preferably randomaccess memory (RAM), and may also include a secondary memory 508.Secondary memory 508 may include, for example, a hard disk drive 510and/or a removable storage drive 512, representing a floppy disk drive,a magnetic tape drive, an optical disk drive, or the like. Removablestorage drive 512 reads from and/or writes to a removable storage unit816 in a well-known manner. Removable storage unit 516 represents afloppy disk, magnetic tape, optical disk, or the like, which is read byand written to by removable storage drive 512. As will be appreciated bypersons skilled in the relevant, art(s), removable storage unit 516includes a computer usable storage medium having stored therein computersoftware and/or data.

In alternative implementations, secondary memory 508 may include othersimilar means for allowing computer programs or other instructions to beloaded into computer system 500. Such means may include, for example, aremovable storage unit 518 and an interface 514. Examples of such meansmay include a program cartridge and cartridge interface (such as thatfound in video game devices), a removable memory chip (such as an EPROM,or PROM) and associated socket, a thumb drive and USB port, and otherremovable storage units 518 and interfaces 514 which allow software anddata to be transferred from removable storage unit 518 to computersystem 500.

Computer system 500 may also include a communications interface 520.Communications interface 520 allows software and data to be transferredbetween computer system 500 and external devices. Examples ofcommunications interface 520 may include a modem, a network interface(such as an Ethernet card), a communications port, a PCMCIA slot andcard, etc. Software and data transferred via communications interface520 are in the form of signals which may be electronic, electromagnetic,optical, or other signals capable of being received by communicationsinterface 520. These signals are provided to communications interface520 via a communications path 522. Communications path 522 carriessignals and may be implemented using wire or cable, fiber optics, aphone line, a cellular phone link, an RF link and other communicationschannels.

As used herein, the terms “computer program medium” and “computerreadable medium” are used to generally refer to tangible storage mediasuch as removable storage units 516 and 518 or a hard disk installed inhard disk drive 510. These computer program products are means forproviding software to computer system 500.

Computer programs (also called computer control logic) are stored inmain memory 506 and/or secondary memory 508. Computer programs may alsobe received via communications interface 520. Such computer programs,when executed, enable the computer system 500 to implement the presentdisclosure as discussed herein. In particular, the computer programs,when executed, enable processor 504 to implement the processes of thepresent disclosure, such as any of the methods described herein.Accordingly, such computer programs represent controllers of thecomputer system 500. Where the disclosure is implemented using software,the software may be stored in a computer program product and loaded intocomputer system 500 using removable storage drive 512, interface 514, orcommunications interface 520.

In another embodiment, features of the disclosure are implementedprimarily in hardware using, for example, hardware components such asapplication-specific integrated circuits (ASICs) and gate arrays.Implementation of a hardware state machine so as to perform thefunctions described herein will also be apparent to persons skilled inthe relevant art(s).

5. Conclusion

Embodiments have been described above with the aid of functionalbuilding blocks illustrating the implementation of specified functionsand relationships thereof. The boundaries of these functional buildingblocks have been arbitrarily defined herein for the convenience of thedescription. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the disclosure that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent disclosure. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

What is claimed is:
 1. A transceiver, comprising: a transmitter operableto up-convert and amplify a transmit baseband signal to provide atransmit RF signal for a small cell base station; a receiver operable toamplify and down-convert a receive RF signal to provide a receivebaseband signal for the small cell base station, wherein the transmit RFsignal is wirelessly transmitted over a same time and frequency band asthe receive RF signal is wirelessly received; and a baseband cancelerconfigured to cancel self-interference from the transmit RF signal inthe receive RF signal at baseband using a distorted copy of the transmitbaseband signal.
 2. The transceiver of claim 1, wherein the basebandcanceller is configured to generate the distorted copy of the transmitbaseband signal based on a non-linear distortion associated with theup-conversion and the amplification performed by the transmitter.
 3. Thetransceiver of claim 1, wherein the baseband canceller is configured tocancel the self-interference from the transmit RF signal in the receiveRF signal at baseband in the digital domain.
 4. The transceiver of claim1, wherein the frequency band is 60 GHz.
 5. The transceiver of claim 1,wherein the frequency band is a millimeter radio band between 30 GHz and300 GHz.
 6. The transceiver of claim 1, wherein the transmit RF signalis wirelessly transmitted to a macro base station, and the receive RFsignal is wirelessly received from the macro base station.
 7. Thetransceiver of claim 6, wherein the macro cell base station has accessto a core network via a wired connection.
 8. The transceiver of claim 1,wherein the transceiver is operable coupled to a directional antenna. 9.A transceiver for small cell backhaul applications, comprising: atransmitter configured to up-convert and amplify a transmit basebandsignal to provide a transmit RF signal; a receiver configured to amplifyand down-convert a receive RF signal to provide a receive basebandsignal, wherein the transmit RF signal is wirelessly transmitted over asame time and frequency band as the receive RF signal is wirelesslyreceived; and a baseband canceller configured to cancelself-interference from the transmit RF signal in the receive RF signalat baseband based on a distorted copy of the transmit baseband signal,wherein no cancellation of the self-interference from the transmit RFsignal in the receive RF signal is performed at RF.
 10. The transceiverof claim 9, wherein the baseband canceller is configured to generate thedistorted copy of the transmit baseband signal based on non-lineardistortions associated with the up-conversion and amplificationperformed by the transmitter on the transmit baseband signal.
 11. Thetransceiver of claim 9, wherein the baseband canceller is configured tocancel the self-interference from the transmit RF signal in the receiveRF signal at baseband in the digital domain.
 12. The transceiver ofclaim 9, wherein the frequency band is 60 GHz.
 13. The transceiver ofclaim 9, wherein the frequency band is a millimeter radio band between30 GHz and 300 GHz.
 14. The transceiver of claim 9, wherein the transmitRF signal is wirelessly transmitted to a macro base station, and thereceive RF signal is wirelessly received from the macro base station.15. The transceiver of claim 14, wherein the macro cell base station hasaccess to core network via a wired connection.
 16. The transceiver ofclaim 9, wherein the transceiver is operably coupled to a directionalbackhaul transmit antenna and a directional backhaul receive antenna.